In vitro Potential of Extract of Ringworm Bush (Cassia alata L.) and Antagonistic Fungi to Control Plant Pathogenic Fungi

Abstract

At present, there are numerous reports on using plant extracts integrated with biological control
agents (BCAs) to control plant diseases. However, before employing this particular alternative measure,
plant extract should be tested to make sure that its fungicidal properties will not be toxic to BCAs.
Therefore, this experiment was conducted to test the in vitro efficacy of extract of ringworm bush
(Cassia alata) at different concentrations (5000, 10000 and 20000 ppm) against 6 genera of plant
pathogenic fungi (Alternaria sp., Curvularia sp., Fusarium sp., Helminthosporium sp., Pestalotia sp. and
Rhizoctonia sp.) as well as on antagonistic fungi except non-pathogenic Fusarium oxysporum F221-B
which was previously reported to be tolerant to pressed juice of ring worm bush. Then, performances of
all test antagonistic fungi (5 isolates of Trichoderma harzianum and F221-B) in combination with ringworm bush extract were investigated using dual culture test on poisoned food medium. The results showed that
the ringworm bush extract at concentrations revealed antifungal activity against mycelial growth and spore
germination of all tested pathogens in the range of 16-53 and 32-94 percent, respectively. The higher the
extract concentration, the more the inhibition effect on pathogens occurred. Moreover, the test extract was
not shown to be toxic to all tested isolates of Trichoderma. Regard to combined application, the result
revealed that performance of Trichoderma isolates combined with the extract in inhibiting the tested
pathogens (in the range of 45.3-69.6 percent) was shown less effective than that of Trichoderma alone.